Variable lift hydraulic valve lifter

ABSTRACT

A hydraulic valve lifter which has its effective length varied by application of the varying hydraulic pressures of the engine lubricating oil so that the effective length of the lifter is the least at low speed and the greatest at high speeds. The effective length of the hydraulic lifter varies the lift and consequently the duration of lift of the valves so that at high speeds the valves open wider and stay open for a greater percentage of each cycle of the engine. The hydraulic lifter has a cylindrical central bore in which are positioned free pistons arranged to receive lubricating oil under pressure therebetween. The higher the pressure the greater the distance the pistons will be separated until a maximum separation is attained. One of the pistons engages the bottom of the bore in the lifter while the other engages the lower end of the push rod. The two pistons are freely movable in the bore and also provide a cushioning connection between the lifter and push rod. In a modified form of the invention, the upper piston is ported to provide lubricating oil to the push rod and the valve stem.

United States Patent [1 1 [1 1 3,742,921 Rendine July 3, 1973 4] VARIABLE LIFT HYDRAULIC VALVE [57 ABSTRACT LIFTER Inventor: Michael J. Rendine, 4161 Leafback Place, Dayton, Ohio 45424 Filed: July 23, 1971 Appl. No.: 165,642

[56] References Cited UNITED STATES PATENTS 5/1960 VoOrhies 123/9055 X l/1970 Shunta et al..... 123/9055 X 4/1960 Williams 123/9055 X 7/1954 Voorhies 123/9055 Primary Examiner-Carlton R. Croyle Assistant ExaminerMichael Koczo, Jr. A!t0rneyBerman et al.

A hydraulic valve lifter which has its effective length varied by application of the varying hydraulic pressures of the engine lubricating oil so that the effective length of the lifter is the least at low speed and the greatest at high speeds. The effective length of the hydraulic lifter varies the lift and consequently the duration of lift of the valves so that at high speeds the valves open wider and stay open for a greater percentage of each cycle of the engine. The hydraulic lifter has a cylindrical central bore in which are positioned free pistons arranged to receive lubricating oil under pressure therebetween. The higher the pressure the greater the distance the pistons will be separated until a maximum separation is attained. One of the pistons engages the bottom of the bore in the lifter while the other engages the lower end of the push rod. The two pistons are freely movable in the bore and also provide a cushioning connection betweenthe lifter and push rod.

In a modified form of the invention, the upper piston the valve stem.

6 Claims, 14 Drawing Figures BACKGROUND OF THE INVENTION FIELD OF THE INVENTION DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to the drawings in detail wherein like The present invention relates to a variable lift reference characters indicate llke parts throughout the draulic valve lifter for internal combustion engines.

SUMMARY OF THE INVENTION A hydraulic valve lifter includes a generally cylindri- 1 port in the engine to receive lubricating oil therefrom under pressure. The lubricating oil flows to the bore in the lifter between the two pistons so as to separate the pistons by hydraulic pressure. The greater the hydraulic pressure the greater the separation of the pistons until the limit of separation is reached. Reciprocation of the lifter due to the action of the cam shaft causes a similar reciprocation of the pistons therein, with the upper piston engaging the push rod to transmit the motion thereto. Under low speed pressure conditions, the pistons are substantially less than their maximum spaced apart'condition and lift the push rod a relatively short amount. With the engine moving at medium speeds, the pistons are further apart and the lift of the push rod is greater. With the engine operating at maximum speeds with maximum pressure on the lubricating oil, the pistons are further apart and provide the greatest lift for the push rod.

In a modified form of the invention, the upper piston is ported to feed lubricating oil to the push rod and thence to the valve stem.

The primary object of the invention is to provide a hydraulic valve lifter with a variable lift controlled by the pressure on the lubricating oil of the engine so that the lift of the valve and the duration thereof is increased as the pressure on the lubricating oil increases at higher speeds.

Other objects and advantages will become apparent from the following specification when considered in the light of the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a vertical sectional view taken through invention illustrating the starting position of the hydraulic lifter when operating at low engine speeds;

FIG. 2 is a view similar to FIG. 1 of the hydraulic lifter in lifted position when operating at medium engine speeds;

FIG. 3 is a view similar to FIG. I of the lifter in beginning position at high speed engine operation;

FIG. 4 is a fragmentary sectional view of a modified I form of the invention;

FIG. 5 is a sectional view of another modified form of the invention;

FIGS. 6, 7 and 8 are sectional views illustrating the position of the lifter and its associated pistons at three cam positions during low speed operation of the enseveral figures, the reference numeral 20 indicates generally a variable lift hydraulic valve lifter constructed in accordance with the invention.

The lifter 20 is adapated for use with an internal com- 0 bustion engine fragmentarily shown at 21. The engine 21 is conventional and has a bore 22 extending therein in aligned relation with a cam lobe 23 on a cam shaft 24. A lubricating oil port 25 opens into the bore 22 intermediate its upper and lower ends.

A generally cylindrical hydraulic lifter 26 is mounted for reciprocation in the bore 22 with its lower end 27 in contact with the cam lobe 23 of the cam shaft 24. The hydraulic lifter 26 has an annular groove 28 formed therein intermediate its upper and lower ends and communicating with a bore 29 which opens into a cylindrical bore 30 formed axially in the lifter 26. The groove 28 is positioned so as to communicate with the port 25 when the lifter 26 is in its lowermost position.

A bore 31 extends axially from the inner end of the bore 30 and terminates at a point spaced well above the lower end 27 of the lifter 26. A port 32 opens from the bore 31 through the lower end 27 of the lifter 26 for reasons to be assigned.

A piston 33 is slidably mounted in the bore 30 and has a cylindrical extension 34 on its lower end slidably mounted in the bore 31. A relatively short spring retainer extension 35 is integrally formed on the lower end of the extension 34 to engage in the upper end of a compression coil spring 36 seated in the bore 31. The coil spring 36 normally urges the piston 33 upwardly in the bore 30. A second piston 37 is mounted for sliding movement in the bore 30 above the piston 33. A lock ring 38 engages in an annular groove 39 in the upper end of the bore 30 to secure the pistons 37, 33 therein.

A compression coil spring 40 is positioned in the bore 30 between the pistons 33 and 37 to normally urge them apart. A conventional push rod 41 forming part of the engine 21 extends into the bore 30 and contacts the upper face of the piston 37.

While I have described the port 25 as communicating with the lubricating oil under normal engine pressure, it should be understood that an oil pressure control device may be installed in the engine to control the pressure of the lubricating oil reaching the valve lifter 26 so as to more closely control the operation of the valve lifter 26.

In the use and operation of the invention with the engine 21 operating at low speed, oil pressure flows through the port 25 into the groove 28 and through the port 29 into the bore 30 between the piston 33 and the piston 37. The piston 37, under these conditions, will normally be engaged against the stop ring 38 and the piston 33 will be spaced well above the lower end 27 of the lifter 26. The spring 36 will maintain the piston 33 in its raised position, as illustrated in FIG. I, and the spring 40, engaging between the pistons 33, 37, will maintain the piston 37 in engagement with the lock ring 38. The pressure of the oil in the bore 30 at low speed operation of the engine is not sufficient to overcome the pressure of the spring 36 and hence the piston 33 and the piston 37 remain in their raised positions, as illustrated in FIG. I. As the cam shaft 24 rotates the cam lobe 23 raises the valve lifter 26 in the bore 22 and the groove 28 moves upwardly out of communication with the bore 25, sealing the oil under pressure in the bore 30 between the pistons 33 37. As the lifter 26 is raised further by the cam lobe 23, the pressure of the push rod 41 against the piston 37 exceeds the pressure of the spring 36 so that the valve lifter 26 moves upwardly in the bore 22 with the pistons 37, 33 remaining for a time at the same height. As the valve lifter 26 continues to move upwardly, the shoulder 42 formed at the juncture of the bores 30, 31 engages the lower face of the piston 33 and raises the piston 33 therewith. The oil, being locked in the bore 30, then exerts a pressure on the piston 37 sufficient to overcome the resistance of the push rod 41 and thus moves the push rod 41 upwardly.

The bore 32 through the bottom of the valve lifter 26 vents the bore 31 and permits the escape of any oil which might seep by the piston 33.

In FIGS. 6, 7 and 8 a low position, medium position and high position of the valve lifter 26 is illustrated with the engine operating at low speeds. It should be noted that the distance between the piston 34 and the piston 37 remains constant during the rotation of the cam lobe 23 with the valve lifter 26 moving to follow the cam lobe 23. To the left of FIG. 8, a pair of lines between opposed arrows indicate the total lift given to the push rod 41 at the highest point of the lobe 23.

In FIGS. 9, and 11 a medium speed operation of the engine is illustrated with three positions of lift of the cam lobe 23. The pressure through the port into the bore during medium speed operation of the engine is sufficient to partially overcome the compression of the spring 36 to thus move the piston 37 and the piston 34 apart a distance slightly greater than the distance illustrated in FIGS. 6 through 8 for low speed operation. With the piston 37 and the piston 34 locked slightly further apart, the piston 37 remains higher with respect to the valve lifter 26 and hence the total lift is greater, as indicated to the left of FIG. 11 by the lines between opposed arrows.

In FIGS. 12 through 14, the highest speed is illustrated with the highest oil pressure. The oil pressure through the port 25 at high engine speeds is sufficient to completely overcome the compression of the spring 36, thus forcing the piston 34 down against the shoulder 42 while the piston 37 is engaged with the lock ring 38. Now, as the cam lobe 23 starts lifting the lifter 26, the piston 37 remains against the lock ring 38 and the total lift to the push rod 41 is greater due to the higher position of the piston 37 in the lifter 26. The total lift of the lifter 26 at high speed engine operation is illustrated to the left of FIG. 14 by the'pair of lines between the opposed arrows.

It should be noted that if separate controls are provided for the oil pressure reaching the bore 30, it would be possible to reduce the oil pressure on deceleration of the engine so as to limit the intake valves to a minimum lift to thus enhance fuel economy and reduce blow by exhaust emission, normally encountered.

In FIG. 4 the engine 121 has a port 143 communicating with the lubricating oil under pressure of the engine. The hydraulic valve lifter 126 has a port 144 communicating with the port 143 when the lifter 126 is in its lowermost position. The upper piston 137 has an annular groove 145 communicating with one end of a radial bore 146 extending into the piston 137. An axial bore 147 communicates with the upper end of the piston 137 and with the inner end of the bore 146. A valve lifter 141 has an axial bore 148 extending therethrough and communicating with the bore 147.

The function of the modification illustrated in FIG. 4 is to lubricate the push rod, valve stem and other valve elements requiring lubrication.

In FIG. 5, another modified form of the invention is illustrated generally at 220 and includes a valve lifter 226 having a bore 230 extending axially therein. A piston 233 is mounted for reciprocation in the bore 230 and has an extension 234 on its lower end. The extension 234 engages in a bore 231 which extends axially of the bore 230 and supports a compression spring 236. A bore 230A, slightly larger than the bore 230, extends inwardly from the upper end of a lifter 226 and has a piston 237 mounted for reciprocation therein. A shoulder 249 between the bore 230 and the bore 230A limits the inward movement of the piston 237 and a lock ring 238 engaged in a groove 239 in the bore 230A limits the outward movement of the piston 237. The annular groove 228 in the valve lifter 226 communicates with a port 229 extending into the bore 230 between the pistons 237 and 233. The limit of the inward movement of the piston 237 by the shoulder 249 eliminates the need for a spring 40 such as is disclosed in the preferred form of the invention. The use and operation of the valve lifter 220 is identical in every respect to the valve lifter 20 with the exception that the spring 40 and its function have been eliminated.

Having thus described the preferred embodiments of the invention, it should be understood that numerous structural modifications and adaptations may be resorted to without departing from the spirit of the invention.

What is claimed is:

1. In an engine of the type including exhaust and intake valves operated by a push rod, and a cam shaft having cam lobes, a variable lift hydraulic lifter in combination therewith comprising a cylindrical lifter body mounted for reciprocation in said engine having its lower end in engagement with said cam lobe of said cam shaft, a port in said engine communicating engine oil under engine induced pressure to said body, an annular groove in the outer cylindrical surface of said body intermediate the opposite ends thereof adapted to communicate with said port when said body is in its lowermost position only, an axial bore in said body opening through the upper end thereof, a bore comm unicating said axial bore with said annular groove, first and second spaced apart pistons mounted for sliding movement in said axial bore in said body respectively above and below said port, the first of said pistons positioned adjacent the open end of said axial bore and adapted to engage said push rod and a stop mounted in said axial bore adjacent the open end thereof, the second of said pistons positioned adjacent the closed inner end of said axial bore and normally spring biased toward said first piston, whereby on operation of said engine on slow speeds oil is pumped between the pistons at a low pressure insufficient to overcome the spring bias of said second piston and rotation of said cam lobe moves said body to move said annular groove out of registry with said port to lock the oil in the axial bore in said body between said pistons to fix the effective length of said lifter, on operation of said engine at a medium speed the oil pressure is higher and a portion of the spring bias is overcome to lengthen the effective length of said lifter and on operation of said engine at a high speed the oil pressure is higher and all of the spring bias is overcome to further lengthen the effective length of said lifter.

2. A device as claimed in claim 1, wherein means are provided for normally maintaining said pistons in spaced apart relation.

3. A device as claimed in claim 2, wherein said means for maintaining said pistons in spaced apart relation comprises a coil spring positioned between said pistons in engagement at each end with said pistons.

4. A device as claimed in claim 2, wherein a shoulder is formed in said bore to limit the inward movement of therewith. 

1. In an engine of the type including exhaust and intake valves operated by a push rod, and a cam shaft having cam lobes, a variable lift hydraulic lifter in combination therewith comprising a cylindrical lifter body mounted for reciprocation in said engine having its lower end in engagement with said cam lobe of said cam shaft, a port in said engine communicating engine oil under engine induced pressure to said body, an annular groove in the outer cylindrical surface of said body intermediate the opposite ends thereof adapted to communicate with said port when said body is in its lowermost position only, an axial bore in said body opening through the upper end thereof, a bore communicating said axial bore with said annular groove, first and second spaced apart pistons mounted for sliding movement in said axial bore in said body respectively above and below said port, the first of said pistons positioned adjacent the open end of said axial bore and adapted to engage said push rod and a stop mounted in said axial bore adjacent the open end thereof, the second of said pistons positioned adjacent the closed inner end of said axial bore and normally spring biased toward said first piston, whereby on operation of said engine on slow speeds oil is pumped between the pistons at a low pressure insufficient to overcome the spring bias of said second piston and rotation of said cam lobe moves said body to move said annular groove out of registry with said port to lock the oil in the axial bore in said body between said pistons to fix the effective length of said lifter, on operation of said engine at a medium speed the oil pressure is higher and a portion of the spring bias is overcome to lengthen the effective length of said lifter and on operation of said engine at a high speed the oil pressure is higher and all of the spring bias is overcome to further lengthen the effective length of said lifter.
 2. A device as claimed in claim 1, wherein means are provided for normally maintaining said pistons in spaced apart relation.
 3. A device as claimed in claim 2, wherein said means for maintaining said pistons in spaced apart relation comprises a coil spring positioned between said pistons in engagement at each end with said pistons.
 4. A device as claimed in claim 2, wherein a shoulder is formed in said bore to limit the inward movement of one of said pistons to provide the means for maintaining said pistons in spaced apart relation.
 5. A device as claimed in claim 8 , wherein said spring biasing of said second piston includes a coil spring seated in a bore formed in said body at the base of said first-named bore to normally urge the second of said pistons toward the first of said pistons.
 6. A device as claimed in claim 1, wherein means are provided in one of said pistons for supplying lubricating oil under pressure to the push rod of an engine used therewith. 